1. Field of the Invention
The present invention relates to a method used in a communication device in a wireless communication system, and more particularly, to a method of radio bearer establishment in dual connectivity.
2. Description of the Prior Art
3GPP in Release 12 proposes dual connectivity for increasing user's throughput. Dual connectivity to at least two cells may be served by different evolved NodeBs (eNB), linked with non-ideal backhaul, e.g., there may be an eNB in charge of a cluster of cells. Therefore, a user equipment (UE) may be served by multiple eNBs when it is in dual connectivity mode.
Under framework of the dual connectivity, a procedure of inter-node radio resource aggregation (INRRA) is proposed to build a UE's connection with more than one node. The INRRA can provide traffic load sharing between the network nodes and improve per-user throughput by utilizing radio resources in more than one node. In other words, the UE may receive different data and service from more than one network nodes. Note that, a node or a network node could be referred to an eNB in this article.
Moreover, different service and different data may have different quality of service (QoS) requirements. In INRRA, traffic streams may be split over more than one network node depending on QoS requirements of each traffic type, loading situation, channel condition, and the combination thereof. In other words, a radio bearer may exist on more than one network node. Multiple network nodes need to maintain the QoS of the radio bearers.
However, the applicant notices that there is no specification for radio bearer establishment on multiple network nodes. Therefore, data transmission/reception to/from more than one network nodes cannot be realized.